Stoplists or stopwords are a list of words that should not be included in further analysis. Usually, this is because they're so common that they don't add much information to the analysis.

These lists are usually dominated by what are known as function words—words that have a grammatical purpose in the sentence, but which themselves do not carry any meaning. For example, the indicates that the noun that follows is singular, but it does not have a meaning by itself. Others prepositions, such as after, have a meaning, but they are so common that they tend to get in the way.

On the other hand, chair has a meaning beyond what it's doing in the sentence, and in fact, it's role in the sentence will vary (subject, direct object, and so on).

You don't always want to use stopwords since they throw away information. However, since function words are more frequent than content words, sometimes focusing on the content words can add clarity to your analysis and...